A partial seizure is a seizure that starts in one specific area of the brain rather than across the entire brain at once. The medical community now calls these “focal seizures,” a name change introduced in 2017 to make the terminology more self-explanatory. The older terms “simple partial seizure” and “complex partial seizure” are still widely used by patients and even some doctors, but they map directly onto the updated categories: focal seizures with preserved consciousness and focal seizures with impaired consciousness.
Focal seizures are the most common type of epilepsy. In a large population study of children and young people with epilepsy, 61% had focal epilepsy, compared to 24% with generalized epilepsy. The same pattern holds in adults. What makes focal seizures tricky is that they look very different depending on which part of the brain is involved, and some are so subtle that people don’t recognize them as seizures at all.
How Focal Seizures Differ From Generalized Seizures
The key distinction is where the electrical misfiring begins. In a generalized seizure, abnormal electrical activity engages both sides of the brain from the start, which is why generalized seizures typically cause full-body convulsions or widespread loss of awareness. A focal seizure begins in one localized network on one side of the brain. The symptoms you experience depend entirely on which brain region is firing: the area that controls movement, sensation, vision, emotion, or memory.
Sometimes a focal seizure stays contained in its starting area. Other times, the abnormal electrical activity spreads outward and eventually involves both hemispheres, at which point it becomes what’s called a “focal to bilateral tonic-clonic seizure.” This is essentially a focal seizure that escalates into a full convulsion. If someone only witnesses the convulsive phase, it can be mistaken for a generalized seizure, which is why accurate diagnosis matters.
Focal Seizures With Preserved Consciousness
Previously called “simple partial seizures,” these are episodes where you remain fully aware and can remember everything that happened. You stay alert and responsive throughout, even though something clearly abnormal is happening in your brain. These seizures often last just seconds to a minute and can be so subtle that other people don’t notice anything unusual.
The symptoms fall into several categories depending on which brain area is involved:
- Motor symptoms: involuntary jerking or twitching in one hand, arm, leg, or one side of the face. The movements are rhythmic and can’t be stopped voluntarily.
- Sensory symptoms: tingling, numbness, or unusual sensations in part of the body. Some people experience visual disturbances, strange smells, odd tastes, or distorted hearing.
- Autonomic symptoms: sudden changes in heart rate, blood pressure, sweating, skin flushing, or a rising sensation in the stomach.
- Emotional symptoms: a sudden wave of fear, dread, anxiety, or occasionally pleasure that comes out of nowhere. Some focal seizures cause involuntary laughing or crying.
- Cognitive symptoms: déjà vu (feeling you’ve experienced something before), jamais vu (feeling that something familiar is suddenly strange), or brief hallucinations.
Many people with focal epilepsy experience an “aura” before a larger seizure. An aura is actually a focal seizure with preserved consciousness. It might feel like a wave of nausea, a strange smell, visual changes, or déjà vu. Recognizing your aura pattern can give you a few seconds of warning to sit down or move to a safe place before a seizure progresses.
Focal Seizures With Impaired Consciousness
Previously called “complex partial seizures,” these involve some degree of reduced awareness. You may not respond normally to people around you, and you often can’t remember the episode afterward. Consciousness is considered impaired if either of those components, recall or responsiveness, is affected at any point during the seizure, even if you were fully aware at the start.
These seizures commonly last longer than 30 seconds, typically one to two minutes, though some can stretch to 10 minutes. A hallmark feature is automatisms: repetitive, purposeless movements that the person performs without being aware of them. Lip-smacking, chewing, swallowing, hand-wringing, picking at clothes, or fumbling with nearby objects are the most common. These automatisms show up in roughly 40% to 80% of people with temporal lobe epilepsy, the most frequent source of focal seizures with impaired consciousness.
During one of these episodes, the person may look awake but seem confused, stare blankly, wander, or respond to questions with garbled words. Afterward, there’s usually a period of confusion or grogginess that can last several minutes. The person often has no memory of what happened during the seizure.
What Causes Focal Seizures
Focal seizures arise from a specific area of brain tissue that has become prone to generating abnormal electrical bursts. In adults, the most common identifiable cause is stroke, which accounts for roughly 42% of focal seizure cases in one large study. Brain infections are the next most common cause at about 27%, followed by brain tumors at around 15%. Traumatic brain injury, areas of old brain damage (scarring from prior injury or infection), and metabolic disorders round out the remaining causes.
In about 5% to 22% of cases, no clear structural cause is found, and the seizures are classified as having an unknown origin. In children, the picture shifts somewhat. Genetic factors and developmental brain differences play a larger role, while stroke and tumors are less common. Some childhood focal epilepsy syndromes are relatively benign and may be outgrown by adolescence.
How Focal Seizures Are Diagnosed
An EEG (electroencephalogram) is the primary tool for confirming focal seizures and pinpointing where they start. The test records electrical activity across the scalp, and in focal epilepsy, it picks up characteristic spike or sharp-wave patterns concentrated over one brain region. Spikes over the temporal region, for instance, are strongly associated with temporal lobe epilepsy. Sometimes the abnormal patterns only appear during sleep or during a prolonged monitoring session, so a routine 20-minute EEG may come back normal even if you do have focal epilepsy.
Brain imaging, usually an MRI, is recommended for anyone with new-onset focal seizures. The goal is to identify a structural cause like a tumor, scar tissue, a vascular malformation, or evidence of a past stroke. Finding a visible lesion helps guide treatment decisions and can determine whether surgery is an option down the line.
Treatment for Focal Seizures
Most people with focal seizures are treated with anti-seizure medication, and many achieve good control with a single drug. The two most effective first-line options are lamotrigine and levetiracetam, both of which have strong evidence for controlling focal seizures while being well tolerated. If neither works well enough or causes problematic side effects, second-line options include carbamazepine, oxcarbazepine, and zonisamide.
Finding the right medication often involves some trial and adjustment. Your doctor will typically start with one drug at a low dose and increase gradually. If the first medication doesn’t control seizures adequately, a second drug may be tried alone or added on. About one-third of people with epilepsy continue to have seizures despite trying multiple medications. For those with drug-resistant focal epilepsy, surgery to remove the area of brain tissue generating the seizures can be highly effective, particularly when imaging and EEG clearly identify a single seizure focus. Nerve stimulation devices are another option for people who aren’t surgical candidates.
What to Do if Someone Has a Focal Seizure
If the person is fully aware (a focal seizure with preserved consciousness), they usually don’t need physical help, just reassurance. If they seem confused, unresponsive, or are performing repetitive movements, they’re likely having a focal seizure with impaired consciousness. Stay calm and stay with them. Guide them away from hazards like traffic, stairs, or sharp objects, but don’t restrain them or try to stop their movements.
If they’re lying down, gently roll them onto their side with their mouth pointing toward the ground to keep the airway clear. Don’t put anything in their mouth. Time the seizure. If it lasts longer than five minutes, or if a second seizure follows quickly without recovery in between, call 911. Once the seizure ends and the person becomes alert, explain what happened calmly. They may be disoriented and have no memory of the episode. Offer to help them get home safely or contact someone for them.